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$NetBSD: patch-src-fontfile-decompress.c,v 1.1 2011/08/18 22:58:24 joerg Exp $
Fix buffer overflow in LZW handler.
--- src/fontfile/decompress.c.orig 2010-06-23 11:18:18.000000000 +0000
+++ src/fontfile/decompress.c
@@ -99,7 +99,7 @@ static char_type magic_header[] = { "\03
#define FIRST 257 /* first free entry */
#define CLEAR 256 /* table clear output code */
-#define STACK_SIZE 8192
+#define STACK_SIZE 65300
typedef struct _compressedFILE {
BufFilePtr file;
@@ -180,14 +180,12 @@ BufFilePushCompressed (BufFilePtr f)
file->tab_suffix[code] = (char_type) code;
}
file->free_ent = ((file->block_compress) ? FIRST : 256 );
+ file->oldcode = -1;
file->clear_flg = 0;
file->offset = 0;
file->size = 0;
file->stackp = file->de_stack;
bzero(file->buf, BITS);
- file->finchar = file->oldcode = getcode (file);
- if (file->oldcode != -1)
- *file->stackp++ = file->finchar;
return BufFileCreate ((char *) file,
BufCompressedFill,
0,
@@ -232,9 +230,6 @@ BufCompressedFill (BufFilePtr f)
if (buf == bufend)
break;
- if (oldcode == -1)
- break;
-
code = getcode (file);
if (code == -1)
break;
@@ -243,19 +238,29 @@ BufCompressedFill (BufFilePtr f)
for ( code = 255; code >= 0; code-- )
file->tab_prefix[code] = 0;
file->clear_flg = 1;
- file->free_ent = FIRST - 1;
- if ( (code = getcode (file)) == -1 ) /* O, untimely death! */
- break;
+ file->free_ent = FIRST;
+ oldcode = -1;
+ continue;
}
incode = code;
/*
* Special case for KwKwK string.
*/
if ( code >= file->free_ent ) {
+ if ( code > file->free_ent || oldcode == -1 ) {
+ /* Bad stream. */
+ return BUFFILEEOF;
+ }
*stackp++ = finchar;
code = oldcode;
}
-
+ /*
+ * The above condition ensures that code < free_ent.
+ * The construction of tab_prefixof in turn guarantees that
+ * each iteration decreases code and therefore stack usage is
+ * bound by 1 << BITS - 256.
+ */
+
/*
* Generate output characters in reverse order
*/
@@ -270,7 +275,7 @@ BufCompressedFill (BufFilePtr f)
/*
* Generate the new entry.
*/
- if ( (code=file->free_ent) < file->maxmaxcode ) {
+ if ( (code=file->free_ent) < file->maxmaxcode && oldcode != -1) {
file->tab_prefix[code] = (unsigned short)oldcode;
file->tab_suffix[code] = finchar;
file->free_ent = code+1;
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